Nonvolatile memory devices, such as Flash storage devices, retain data even after power is removed. This desirable property has led to Flash storage devices being used in memory cards and electronic devices for the storage of data (e.g., contacts in a smartphone) and media files (e.g., audio, video, and image data in a smartphone). The ubiquitousness of such small form factor portable electronic devices, the increasing prevalence and size of media files, and the increasing demand to store such media locally on the portable electronic device in order to have instant access when compared to remote storage solutions has created the “perfect storm” for storage device manufacturers—increase capacity, reduce cost, improve reliability, and reduce storage device footprint to accommodate ever-shrinking device portable electronic device housings.
Three-dimensional NAND (3D NAND) offers a potential solution to the ever increasing demand for storage in electronic devices. Two-dimensional NAND memory is arranged horizontally. Using such an arrangement, physics dictated the minimum spacing between memory cells before electron tunneling and other phenomena affecting the reliability of the storage device occurred. The 3D NAND architecture includes a vertical stack of memory cells, each of which includes: a charge storage structure (floating gate, charge trap, etc.). The stack of memory cells is formed using alternating layers of control gate material and dielectric material. A charge blocking material is disposed between the control gate layer and the charge storage structure associated with the respective cell. The number of control gate layers determine the number of individual storage cells in each vertical 3D NAND structure. Deep stacked 3D NAND structures having 32, 48, or even 72+ control gate layers are possible.
Although the following Detailed Description will proceed with reference being made to illustrative embodiments, many alternatives, modifications and variations thereof will be apparent to those skilled in the art.